A brake force sensor

Abstract

The application relates to a brake force sensor, which comprises a pressure sensing terminal, a sensitive element arranged on the top of the pressure sensing terminal and used for converting a force signal loaded above the sensitive element into an electric signal output, a support arranged on the sensitive element, a printed circuit board fixed on the support and electrically connected with the sensitive element and used for processing the electric signal output by the sensitive element to obtain an output signal, a flexible circuit board arranged on the printed circuit board, a shell arranged on the pressure sensing terminal and covering the sensitive element, the support, the printed circuit board and the flexible circuit board in the shell, and a spring PIN needle, a plurality of spring PIN needles are arranged in the shell, the spring PIN needle is electrically connected with the printed circuit board through the flexible circuit board, and the spring PIN needle is used for contacting the outside world to generate a deformation force and acting on the printed circuit board. The brake force sensor solves the problems of large size, low high-low temperature precision, the need of temperature compensation, poor repeatability and high process difficulty in the prior art.

Description

Technical Field

[0001] This application relates to the field of sensor technology, and more particularly to a braking force sensor. Background Technology

[0002] Force sensors are devices that convert force load signals into easily modulated signals such as electrical signals. They are widely used in hydraulic control, the automotive industry, and aerospace. In the automotive industry, for example, in brake-by-wire systems, the high integration of the system places stringent requirements on sensor size. It's necessary to minimize the sensor's size while ensuring performance and reliability. Furthermore, automotive sensors require conditioned digital SENT signals or 0.5-4.5V voltage signals as their output signals. Therefore, conditioning circuitry must be integrated into the sensor. Additionally, the typical operating temperature range for automotive sensors is -40°C to 125°C, and the sensor must maintain the required accuracy within this temperature range. Moreover, the large volume of automotive sensors used necessitates strict cost control within the automotive industry.

[0003] Chinese patent document CN118168696A discloses a force sensor for pedal force detection and its fabrication method. It employs a spoke-type structure with multiple sensing elements distributed on a corresponding number of cantilever beams. Its advantages include low nonlinearity, low hysteresis, and high accuracy, making it the most commonly used force sensor solution in the industrial field. However, if applied to automotive braking EMB systems to detect the clamping force of the brake caliper during braking, the force sensor's design size would be very large, while the internal space of the brake caliper is limited, making it difficult to meet assembly requirements.

[0004] Chinese patent document CN118541591A discloses a force sensor device for electromechanical brakes, which adopts a ring structure. On one hand, it uses silicon MEMS strain gauges as sensing elements, with four sensing elements sintered and mounted onto the sensing surface using glass micro-fusion technology to sense the stress transmitted from the pressure-sensing element. Because silicon strain gauges have a high zero-point and high sensitivity temperature coefficient, their output signal is very sensitive to temperature changes, resulting in inherently low high and low temperature accuracy, requiring temperature compensation to improve accuracy. On the other hand, the small size of silicon strain gauges cannot cover the entire strain area. Even slight changes in the external force application point will affect the actual sensed stress / strain, leading to different signal output values ​​from the sensing element under the same external force, meaning the sensor's repeatability is relatively poor. Furthermore, this technology requires complex processes such as high-temperature sintering, aluminum wire ultrasonic bonding, high and low temperature compensation calibration, and testing, making the process difficult and the production cost high.

[0005] There is currently no effective solution to the aforementioned problems in the existing technology. Summary of the Invention

[0006] To address the aforementioned issues, this application provides a braking force sensor that solves the problems of large size, low accuracy at high and low temperatures, need for temperature compensation, poor repeatability, and high manufacturing difficulty in the prior art.

[0007] Specifically, the following technical solutions are included:

[0008] This application provides a braking force sensor, including:

[0009] The pressure-sensing terminal is a hollow annular rotating body structure;

[0010] A sensitive element is disposed on the top of the pressure-sensing terminal to convert the force signal applied above it into an electrical signal output.

[0011] A bracket is mounted on the sensitive element;

[0012] A printed circuit board, fixed on the bracket, is electrically connected to the sensitive element and is used to process the electrical signal output by the sensitive element to obtain an output signal;

[0013] Flexible circuit board, mounted on a printed circuit board;

[0014] The housing is disposed on the pressure-sensing terminal and encloses the sensitive element, bracket, printed circuit board and flexible circuit board inside it;

[0015] A number of spring pins are disposed in the housing. The spring pins are electrically connected to the printed circuit board via a flexible circuit board. The spring pins are used to generate deformation force by contacting the outside and acting on the printed circuit board.

[0016] In one embodiment of this application, the pressure-sensitive terminal has a pressure-sensitive area for mounting a sensitive element, a multi-level stepped structure for connecting the bracket and the housing, and a first force loading area for applying external force on the side facing the housing. The pressure-sensitive area is an annular protrusion structure, the multi-level stepped structure is disposed on the outer periphery of the pressure-sensitive area, and the first force loading area is annularly disposed at the edge of the pressure-sensitive terminal facing the housing. The multi-level stepped structure includes an adjacent first step and a second step, the first step being used to connect the bracket, and the second step being used to connect the housing.

[0017] In one embodiment of this application, a second force loading area and a stress buffer groove are provided on the side of the pressure-sensing terminal away from the outer shell. The stress buffer groove is used to release stress, avoid excessive local stress concentration that could cause plastic deformation of the pressure-sensing terminal, and optimize the force transmission direction. The second force loading area is an annular protrusion structure and is located in the middle of the side of the pressure-sensing terminal away from the outer shell. The first force loading area and the second force loading area are used to sense external clamping force and load external forces.

[0018] In one embodiment of this application, a plurality of positioning anti-rotation grooves are provided at the edge of the upper surface and the edge of the lower surface of the pressure-sensing terminal, and the positioning anti-rotation grooves on the upper surface and the lower surface of the pressure-sensing terminal are orthogonally distributed.

[0019] In one embodiment of this application, the inner wall of the pressure-sensing terminal is provided with a mounting groove, a sealing ring is installed in the mounting groove, and the outer shell and the pressure-sensing terminal are sealed together by the sealing ring.

[0020] In one embodiment of this application, the sensitive element is a circular thin sheet that uniformly covers the pressure-sensing area of ​​the pressure-sensing terminal; the pressure-sensing terminal is made of high-strength alloy steel.

[0021] In one embodiment of this application, the sensitive element is bonded to the pressure-sensing terminal with adhesive; the sensitive element is connected to the printed circuit board by wire soldering; the sensitive element is a metal strain gauge.

[0022] In one embodiment of this application, the sensitive element has a three-layer structure, including two substrate layers and a metal foil located between the two substrate layers. The substrate material is polyimide, and the metal foil is selected from constantan, Evan, and Karma alloys.

[0023] In one embodiment of this application, the metal foil is provided with four resistors, including two outer resistors and two inner resistors, which are connected to the outside through six pads; the outer resistors are radially distributed and their resistance direction is parallel to the diameter direction of the annular sheet of the sensitive element; the inner resistors are tangentially distributed and their resistance direction is perpendicular to the diameter direction of the annular sheet of the sensitive element.

[0024] In one embodiment of this application, the outer shell is provided with a plurality of through holes, and a sealing sleeve is provided on the plurality of through holes. The plurality of spring pins pass through the sealing sleeves and are inserted into the plurality of through holes one by one.

[0025] Compared with the prior art, the beneficial effects of this application are:

[0026] 1. The overall structure is adapted to the EMB (Brace-by-Wire) system, which has high dimensional requirements, such as an overall outer diameter of 40mm, a thickness of 15mm, and a force detection range of 0-65000N. Conventional spoke-type structures cannot meet the requirements, and the force sensor with the ring-type structure or similar topology provided in this application must be used.

[0027] 2. The sensing element uses temperature-compensated Evan, Karma, or Constantan alloys, which can ensure that the influence of temperature on the output signal is covered within the accuracy requirements range under the normal operating temperature of automotive sensors from -40 to 150℃, thus effectively guaranteeing the output accuracy of the force sensor.

[0028] 3. The sensitive element signal does not require additional temperature compensation, making the production process of the force sensor relatively simple. It does not require a force calibration system with temperature or a force testing system with temperature.

[0029] 4. The sensitive element is designed as a circular thin sheet that evenly covers the entire strain-sensing area, so it is not easily affected by the offset of the force application point, which can effectively improve the repeatability of the force sensor output signal.

[0030] 5. The sensing terminal adopts a positioning anti-rotation groove design with multiple anti-rotation structures, which can avoid sliding friction between the force sensor and the gasket and bearing during use, prevent the force contact point of the force sensor from being damaged by friction and causing a decrease in accuracy, and improve its long-term force detection accuracy and service life. The sensing terminal has multiple slots and rounded corners; surface slots are used to reduce surface stress concentration; stress buffer grooves are used to avoid stress concentration in the force transmission area and optimize the force transmission direction; multiple rounded corners are used to prevent local stress concentration.

[0031] 6. The conditioning circuit, consisting of an ASIC chip mounted on the printed circuit board, processes the raw voltage signal output by the sensitive element, and can output corresponding digital SENT signals or analog voltage signals. The printed circuit board is electrically connected to the outside via spring pin connectors such as POGO-PIN, which can achieve no transient or short-term transient interruption under the V5 vibration level of the wheel edge, ensuring the reliability of the force sensor in actual use.

[0032] 7. The braking force sensor provided in this application has a lower manufacturing difficulty compared to force sensors based on silicon MEMS glass micro-fusion technology. In this application, the sensitive element is glued to the pressure-sensing terminal, and after curing and aging, it can achieve stable application within the conventional automotive sensor operating temperature range of -40 to 125°C, eliminating the need for the 500-600°C high-temperature glass micro-fusion process. Furthermore, the sensitive element is connected to the printed circuit board using wire bonding, eliminating the need for specialized aluminum wire bonding equipment. Additionally, no temperature compensation calibration and testing system is required. This effectively reduces the sensor's production and manufacturing costs. Attached Figure Description

[0033] Figure 1 An exploded view of the braking force sensor provided in this application.

[0034] Figure 2 A perspective view of the braking force sensor provided in this application.

[0035] Figure 3 A cross-sectional view of the braking force sensor provided by this application.

[0036] Figure 4 A perspective view of the pressure-sensing terminal provided in this application.

[0037] Figure 5 A cross-sectional view of the pressure-sensing terminal provided in this application.

[0038] Figure 6 A top view of the pressure-sensing terminal provided in this application.

[0039] Figure 7 A bottom view of the pressure-sensing terminal provided in this application.

[0040] Figure 8 A top view of the sensitive element provided in this application.

[0041] In the diagram: 1. Pressure-sensing terminal; 11. Mounting groove; 12. Positioning anti-rotation groove; 13. Pressure-sensing area; 14. Multi-stage stepped structure; 141. First step; 142. Second step; 15. First force loading area; 16. Second force loading area; 17. Stress buffer groove; 2. Sealing ring; 3. Sensing element; 31. Outer resistor; 32. Inner resistor; 33. Solder pad; 4. Bracket; 5. Printed circuit board; 6. Flexible circuit board; 7. Housing; 71. Through hole; 8. Sealing sleeve; 9. Spring pin. Detailed Implementation

[0042] The technical solutions of this application will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0043] In the description of this application, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this application. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. The terms "first position" and "second position" refer to two different positions.

[0044] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to fixed connections or detachable connections; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and internal connections between two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0045] like Figures 1 to 8 As shown, this application provides a braking force sensor, which in some embodiments includes:

[0046] Pressure sensing terminal 1, wherein the pressure sensing terminal 1 is a hollow annular rotating body structure;

[0047] Sensing element 3 is disposed on the top of the pressure-sensing terminal 1 and is used to convert the force signal applied above it into an electrical signal output;

[0048] The bracket 4 is disposed on the sensitive element 3;

[0049] The printed circuit board 5 is fixed on the bracket 4 and electrically connected to the sensitive element 3. It is used to process the electrical signal output by the sensitive element 3 to obtain an output signal.

[0050] Flexible circuit board 6 is disposed on printed circuit board 5;

[0051] The outer casing 7 is disposed on the pressure-sensing terminal 1 and encloses the sensitive element 3, the bracket 4, the printed circuit board 5 and the flexible circuit board 6 inside it;

[0052] A number of spring pins 9 are disposed in the housing 7. The spring pins 9 are electrically connected to the printed circuit board 5 through a flexible circuit board 6. The spring pins 9 are used to generate deformation force when in contact with the outside and act on the printed circuit board 5.

[0053] In some embodiments, the inner wall of the pressure-sensing terminal 1 is provided with a mounting groove 11, and a sealing ring 2 is installed in the mounting groove 11. The outer shell 7 and the pressure-sensing terminal 1 are sealed together by the sealing ring 2, thereby achieving environmental sealing.

[0054] In some embodiments, the sensing element 3 is attached to the pressure-sensing terminal 1, and the sensing element 3 is a metal strain gauge.

[0055] Optionally, the bracket 4 is welded to the pressure-sensing terminal 1 by laser welding; the pressure-sensing terminal 1, the bracket 4, and the outer shell 7 are all made of metal.

[0056] In some embodiments, the printed circuit board 5 is equipped with conditioning chips, resistors, capacitors, and other electronic components via reflow soldering, forming a conditioning circuit for modulation and calibration of the force sensor signal. Optionally, the printed circuit board 5 is fixed to the bracket 4 via reflow soldering.

[0057] In this embodiment, the raw voltage signal output by the sensitive element 3 is processed by a conditioning circuit consisting of an ASIC chip mounted on the printed circuit board 5, which can output a corresponding digital SENT signal or an analog voltage signal. The printed circuit board 5 is electrically connected to the outside through a spring pin connector scheme such as POGO-PIN, which can achieve no transient or short-term transient interruption under the V5 vibration level of the wheel edge, ensuring the reliability of the force sensor in actual use.

[0058] In some embodiments, one end of the flexible circuit board 6 is electrically connected to the printed circuit board 5, and the other end is connected to the spring pin 9, thereby realizing the electrical connection between the spring pin 9 and the printed circuit board 5 through the flexible circuit board 6.

[0059] In some embodiments, the outer casing 7 is provided with a plurality of through holes 71, and a sealing sleeve 8 is provided on the plurality of through holes 71. A plurality of spring pins 9 pass through the sealing sleeve 8 and are inserted into the plurality of through holes 71 one by one.

[0060] In this embodiment, the outer casing 7 has three through holes 71, and a sealing sleeve 8 is provided at each through hole 71 to achieve environmental sealing. The sealing sleeve 8 is connected to three spring pins 9, which serve as signal input / output interfaces. Optionally, the outer casing 7 is connected to the pressure-sensing terminal 1 by laser welding.

[0061] In some embodiments, the pressure-sensing terminal 1 is a hollow annular rotating body structure. A plurality of positioning anti-rotation grooves 12 are provided at the edge of the upper surface and the edge of the lower surface of the pressure-sensing terminal 1. The positioning anti-rotation grooves 12 on the upper surface of the pressure-sensing terminal 1 and the positioning anti-rotation grooves 12 on the lower surface of the pressure-sensing terminal 1 are orthogonally distributed.

[0062] In this embodiment, four positioning anti-rotation grooves 12 are provided at the edge of the pressure-sensing terminal 1, two of which are located on the upper surface of the pressure-sensing terminal 1 and are orthogonally distributed with the other two positioning anti-rotation grooves 12 located on the lower surface of the pressure-sensing terminal 1. The positioning anti-rotation grooves 12 are used to ensure the positioning and anti-rotation of the force sensor during production, assembly and use.

[0063] Furthermore, the pressure-sensing terminal 1 has a pressure-sensing area 13 for mounting the sensitive element 3, a multi-level stepped structure 14 for connecting the bracket 4 and the housing 7, and a first force loading area 15 for loading external forces on the side facing the housing 7. The pressure-sensing area 13 is an annular protrusion structure, the multi-level stepped structure 14 is disposed on the outer periphery of the pressure-sensing area 13, and the first force loading area 15 is annularly disposed at the edge of the side of the pressure-sensing terminal 1 facing the housing 7. The multi-level stepped structure 14 includes an adjacent first step 141 and a second step 142. The first step 141 is used to connect the bracket 4, and the second step 142 is used to connect the housing 7.

[0064] In this embodiment, the first step 141 is used for welding the bracket 4, and the second step 142 is used for welding the outer shell 7.

[0065] Furthermore, the pressure-sensing terminal 1 is provided with a second force loading area 16 and a stress buffer groove 17 on the side away from the outer casing 7. The stress buffer groove 17 is used to release stress, avoid excessive local stress concentration which could cause plastic deformation of the pressure-sensing terminal 1, and optimize the force transmission direction. The second force loading area 16 is an annular protrusion structure, and the second force loading area 16 is located in the middle of the side of the pressure-sensing terminal 1 away from the outer casing 7. The first force loading area 15 and the second force loading area 16 are used to sense external clamping force and load external forces.

[0066] Optionally, the pressure-sensing terminal 1 is made of high-strength alloy steel, such as SUS630, which has high yield strength and is suitable for small-sized, high-range force sensor products like those of this invention. If SUS630 alloy steel is used, heat treatment is required, with the standard heat treatment being H900.

[0067] The braking force sensor provided in this application employs a multi-anti-rotation structure with positioning anti-rotation grooves 12 at its sensing terminal 1. This design prevents sliding friction between the force sensor and the gasket or bearing during use, avoids damage to the force contact points of the force sensor due to friction, thus reducing accuracy and improving its long-term force detection accuracy and service life. The sensing terminal 1 features multiple grooves and rounded corners; surface grooves are used to concentrate surface stress; stress buffer grooves 17 prevent stress concentration in the force transmission area and optimize the force transmission direction; and multiple rounded corners prevent localized stress concentration.

[0068] Optionally, the sensitive element 3 is a ring-shaped thin sheet that uniformly covers the pressure-sensing area 13 of the pressure-sensing terminal 1.

[0069] In this embodiment, the sensitive element 3 is designed as a circular thin sheet and uniformly covers the entire strain-sensing pressure area 13. Therefore, it is not easily affected by the offset of the force application point, which can effectively improve the repeatability of the force sensor output signal.

[0070] Optionally, the sensitive element 3 is glued to the pressure-sensitive terminal 1; the sensitive element 3 is connected to the printed circuit board 5 by soldering wires.

[0071] In this embodiment, on the one hand, the sensing element 3 is bonded to the pressure-sensing terminal 1 with adhesive, and after curing and aging, it can achieve stable application within the conventional operating temperature range of automotive sensors (-40 to 125°C), eliminating the need for the 500-600°C high-temperature glass micro-melting process. On the other hand, the sensing element 3 is connected to the printed circuit board 5 using a wire bonding method, eliminating the need for specialized aluminum wire bonding equipment. Furthermore, no temperature compensation calibration and testing system is required. This effectively reduces the production and manufacturing costs of the sensor.

[0072] Furthermore, the sensing element 3 has a three-layer structure, including two substrate layers and a metal foil between the two substrate layers. The substrate material is polyimide with a wide temperature resistance range, covering the automotive sensor's operating temperature range of -40 to 150°C. The metal foil is the core material of the sensing element. Compensation for the temperature coefficient of resistance needs to be considered to ensure a low temperature coefficient of resistance within the automotive sensor's operating temperature range of -40 to 150°C. Simultaneously, a relatively high strain coefficient is also required. Generally, constantan, Evan, or Karma alloys are selected as the metal foil material for the sensing element 3. This ensures that the influence of temperature on the output signal is covered within the accuracy requirements under the normal operating temperature range of -40 to 150°C for automotive sensors, effectively guaranteeing the output accuracy of the force sensor.

[0073] Furthermore, in order to ensure that the output signal of the sensitive element 3 can be processed by the conditioning circuit, the resistance value of the sensitive element 3 should not be too small, usually greater than 1 kΩ, and preferably around 3 kΩ.

[0074] Furthermore, the metal foil is provided with four resistors, including two outer resistors 31 and two inner resistors 32, which are connected to the outside through six pads 33; the outer resistors 31 are radially distributed, that is, the resistance direction of the outer resistors 31 is parallel to the diameter direction of the annular sheet of the sensitive element 3; the inner resistors 32 are tangentially distributed, that is, the resistance direction of the inner resistors 32 is perpendicular to the diameter direction of the annular sheet of the sensitive element 3.

[0075] The direction of the resistance is determined by the simulation structure of the stress and strain distribution on the pressure-sensing terminal 1. That is, the tangential strain is larger near the inside. The inner resistor 32 is also the resistor that plays a dominant role in the output signal among the sensitive elements 3.

[0076] Specifically, the area of ​​the sensitive element 3 above the pressure-sensing terminal 1 experiences stress / strain in different directions when an external force is applied. The stress / strain in the inner resistor 32 area is mainly concentrated in the tangential direction, and its magnitude is approximately one order of magnitude greater than that in the radial direction. Therefore, the resistance of the inner resistor 32 is tangentially distributed, maximizing the sensing of tangential stress / strain and ensuring high sensitivity of the original signal output by the sensitive element 3. Although the stress / strain in the outer resistor 31 area is also mainly concentrated in the tangential direction, and the radial stress / strain is approximately 25% of that in the tangential direction (the signs of radial and tangential stress / strain are opposite), the direction of the outer resistor 31 needs to be set to radial distribution. This is because the sign of the stress / strain in the outer resistor 31 area is the same as that in the inner resistor 32 area. If the outer resistor 31 is set to tangential distribution, it will negatively affect the sensitivity of the overall Wheatstone bridge formed by the inner resistor 32 and the outer resistor 31. Setting it to radial distribution, even though the absolute value of the radially distributed stress / strain is smaller, will still have a positive effect on the sensitivity of the overall Wheatstone bridge. The sensitivity of the Wheatstone bridge will greatly affect the calibration process of subsequent products and the accuracy of the final product.

[0077] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. A brake force sensor, characterized by, The application relates to a pressure sensor, which comprises the following components: a hollow annular rotary body structure of a pressure sensing terminal (1); a sensitive element (3) arranged on the top of the pressure sensing terminal (1) and used for converting a force signal loaded thereon into an electric signal output; a support (4) arranged on the sensitive element (3); a printed circuit board (5) fixed on the support (4) and electrically connected with the sensitive element (3) and used for processing the electric signal output by the sensitive element (3) to obtain an output signal; a flexible circuit board (6) arranged on the printed circuit board (5); a shell (7) arranged on the pressure sensing terminal (1) and covering the sensitive element (3), the support (4), the printed circuit board (5) and the flexible circuit board (6) in the shell (7); a plurality of spring PIN needles (9) arranged in the shell (7), the spring PIN needles (9) being electrically connected with the printed circuit board (5) through the flexible circuit board (6) and being used for contacting the outside world to generate a deformation force and acting on the printed circuit board (5); the sensitive element (3) is a three-layer structure comprising two substrates and a metal foil arranged between the two substrates, the substrate material is polyimide, and the metal foil is selected from the group consisting of constantan, Evan or Karma alloy; four resistors are arranged on the metal foil, including two outer resistors (31) and two inner resistors (32), the four resistors are connected with the outside through six pads (33), the outer resistors (31) are distributed in a radial direction, the resistance direction of the outer resistors (31) is parallel to the diameter direction of the annular sheet of the sensitive element (3), and the inner resistors (32) are distributed in a tangential direction, the resistance direction of the inner resistors (32) is perpendicular to the diameter direction of the annular sheet of the sensitive element (3). One side of the pressure sensing terminal (1) towards the shell (7) is provided with a pressure sensing area (13) for attaching the sensitive element (3), a multi-stage step structure (14) for connecting the support (4) and the shell (7) and a first force loading area (15) for loading the force from the outside world, the pressure sensing area (13) is an annular convex structure, the multi-stage step structure (14) is arranged on the outer periphery of the pressure sensing area (13), and the first force loading area (15) is arranged in a ring shape at the edge of the side of the pressure sensing terminal (1) towards the shell (7); the multi-stage step structure (14) comprises a first step (141) and a second step (142) arranged adjacently, the first step (141) is used for connecting the support (4), and the second step (142) is used for connecting the shell (7). ​ ​ ​ ​ ​ ​ ​ ​ 2. A brake force sensor according to claim 1, wherein ​ 3. A brake force sensor according to claim 2, wherein The pressure sensing terminal (1) is provided with a second force loading area (16) and a stress buffer groove (17) on the side away from the shell (7), the stress buffer groove (17) is used for releasing stress, avoiding excessive concentration of local stress to cause plastic deformation of the pressure sensing terminal (1), and the force transmission direction can be optimized; the second force loading area (16) is a ring-shaped convex structure, and the second force loading area (16) is located at the middle position of the side of the pressure sensing terminal (1) away from the shell (7); the first force loading area (15) and the second force loading area (16) are used for sensing external clamping force and loading external force.

4. A brake force sensor according to claim 3, wherein The edge of the upper surface of the pressure sensing terminal (1) and the edge of the lower surface are provided with a plurality of positioning rotation stopping grooves (12), the positioning rotation stopping grooves (12) on the upper surface of the pressure sensing terminal (1) and the positioning rotation stopping grooves (12) on the lower surface of the pressure sensing terminal (1) are orthogonally distributed.

5. A brake force sensor according to claim 4, wherein The inner wall of the pressure sensing terminal (1) is provided with a mounting groove (11), the mounting groove (11) is mounted with a sealing ring (2), and the shell (7) and the pressure sensing terminal (1) are sealingly connected through the sealing ring (2).

6. A brake force sensor according to claim 5, wherein The sensitive element (3) is a circular ring-shaped sheet and uniformly covers the pressure sensing area (13) of the pressure sensing terminal (1); the pressure sensing terminal (1) is made of high-strength alloy steel.

7. A brake force sensor according to claim 6, wherein The sensitive element (3) is bonded on the pressure sensing terminal (1) by glue; the sensitive element (3) and the printed circuit board (5) are connected by wire welding; the sensitive element (3) is made of a metal strain gauge.

8. The brake force sensor of claim 1, wherein, The shell (7) is provided with a plurality of through holes (71), a plurality of sealing sleeves (8) are arranged on the plurality of through holes (71), and a plurality of spring PIN needles (9) are inserted into the plurality of through holes (71) through the sealing sleeves (8).

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